Monte carlo simulation of velocity as water quality indicator in distribution networks

Water quality is an increasingly important aspect of water distribution network (DN) design and operation. Traditional water quality indicators include regulated disinfectant residuals and disinfection by-products. However, recent research suggests that velocity itself is an important indicator of water quality, especially when it comes to customer complaints. Designing for higher velocities requires some re-Thinking of traditional North American practices, such as minimum pipe diameters, looping, and fire flows. This work examines the influence of increased velocity on the entire distribution of particles observed in DNs using Monte Carlo simulation. It was shown that large fraction of observed particles can settle to the pipe surface in less than one hour. It was also shown that if the pipe experiences a velocity of 0.25 m/s, during high demand periods for example, these particles are expected to be re-suspended. This is consistent with field research and suggests that the sedimentation and re-suspension model can explain important aspects of particle dynamics and turbidity creation in DNs. Considering the entire distribution of particles suggests that the smaller and less dense fractions are preferentially re-suspended and removed from the pipe surface. This has important implications on pipe conditioning, where pipes that experience higher velocities are less prone to turbidity upsets.